Abrasive article



Feb 1937- D. E. WEBSTER; 2,070,764

ABRAS IVE ARTICLE FiledOct. 8, 1934 WITNESSES DUANE E. WE as TER Patented Feb. 16, 1937 ABItAsIvn ARTICLE Duane E. Webster, Worcester, Mass., assignor to Norton Company, Worcester, Mass., acorporation of Massachusetts Application octobe'r 8, 1934, Serial No. 747,325

4 Claims.

This invention relates to a bonded abrasive article and more particularly to a disk shaped grinding wheel especially adapted to perform an abrading operation with its flat side face.

which arise from the great difference occasioned by the coefficients of expansion of the bonded abrasive body and the metal backing plate. Even if no cracks or structural strains are evident when the grinding unit is initially manufactured,

heavy duty grinding operations. Consequently, due to the internal stresses and strains set up during the manufacture of such a grinding wheel, as well as the excessive stresses in such a manner that all of the abrasive material maybe employed for an abrading operation and yet the disk and its backing may be easily and quickly demountably secured to a rotatable pport.

It has been found that certain types of grind- 1 and strains occasioned during a heavy duty 5 ing operations are successfully accomplished by grinding operation, it has been extremely difliengaging the work with the rapidly rotating fiat cult to .permanently cement a bonded abraabrading face of a. disk shaped grinding wheel. sive grinding disk to a rigid backing member One type of grinding disk has nuts imbedded with sufiicient tenacity to withstand the heavy within its rear wheel face in such a manner that duty grinding operations for which a wheel of the wheel may be removably secured to any suitthis shape and type is particularly adapted. able rotatable support by means of screw thread- It has been further proposed to provide a ed bolts engaging the imbedded nuts. In this molded backing member having anchoring detype of grinding unit, the nuts prevents utilizing vices imbedded therein and to cement said backall of the available wheel thickness for a grinding ing member to one of the two opposed flat grindoperation and necessitate discarding and wasting ing wheel faces, whereby suitable clamping dea large portion of each grinding disk when it has vices mayengage the anchoring devices and serve been worn down to the nuts imbedded therein. to removably secure the grinding unit to a suit- Furthermore, it has been found that these imable rotatable support for an abrading operation. bedded nuts frequently work loose during a However, it has been found that these anchoring grinding operation and consequently provide an devices occasionally tear loose and, consequently, insecure support for the grinding wheel, thereby it is necessary to provide a large number of such causing an inaccurate and unsafe grinding opanchoring devices to securely support the grinderation which seriously endangers the safety of ing unit in operative position. These anchoring the machine operator. devices must be precisely located in the backing Another type of grinding wheel adapted for member during its manufacture by means of fiat face grinding has been provided with a rigid, special positioning mechanism which necessitates disk shaped, heavy iron backing plate which is much care and skill. Furthermore, the machine secured to one of the opposed flat annular wheel operator often wastes considerable time in refaces by means of various cements, and this backplacing a new grinding unit, due to the fact that ing plate is bolted to a rotatable support to rehe must remove and replace a large number of movably secure the grinding wheel in operative clamping members to properly secure the grindposition. However, it has been found that in ing unit in position. this type of construction, the backing plates often It is the principal object of this invention to break loose from their grinding wheels or cause overcome the various inherent disadvantages of cracks to develop in the grinding wheels themsuch prior constructions and to provide an abraselves, which result in wheel breakage. sive article and a rigid backing therefor which are y of the m n s e p y d in ecu capable of being easily and inexpensively progrinding wheels to iron backing plates have to be duced and integrally secured together as an inheat-set at relatively high. temperatures which separable unit and quickly, easily and removably 40 frequently result in uneven expansions of the clamped in abrading position. grinding wheel and its backing plate sufiicient to A further object of this invention is to provide cause ruptin'e of the wheel during manufacture. a grinding disk construction including anin- On cooling to room temperature. various stresses expensive, easily molded backing integrally seare set up'in the warm mass due to shrinkage, cured to the side face of a bonded abrasive body these fragile grinding members may stillbe de- Wheels of this type are primarilfiritianded for In accordance with the present invention, it fective due to the internal stresses and strains ispropose'd to constructanabrasive article, adaptoccasioned the fact ring operation; and remain/wheel abrading wherein abonded-abrasive body;

such as" an abrading disk, may be integrally 'se- 56 ed tqpc lorrn an-abrading operation with-a flat}; 1

cured to a backing which in turn supports the abrasive body in operative position. Suitable clamping means such as a clamping plate engageable with the backing serves to demountably secure the r *itire abrasive article upon a support.

In my preferred construction, the backing may comprise a moldable material which may be shaped under pressure into a rigid supporting body, and preferably by a separate molding operation prior to its being secured to the disk. A clamping member 0. plate within the wheel hole either removably or fixedly engages the backing and is arranged to receive clamping devices such as bolts which demountably secure the wheel and its backing to any suitable support. If desired, the molded backing may be further strengthened by reinforcing members such as wires imbedded therein during the molding Operation. The lam inated structure forming the entire grinding wheel is built into an integral unit byrneans of an intermediate sheet of plastic raw rubber compound located between the abrasive body and the backing member. This layer of plastic rubber is vulcanized in situ under the influence of heat and pressure, and the rubber is caused to flow into the pore structure of the abrasive member and unite with the backing, thus integrally securing the backing and abrasive body together as a single, inseparable unit.

In the drawing, which illustrates one embodiment of my invention and in which like numerals indicate like parts:

Fig. 1 is a plan view of a grinding wheel embodying my invention;

Fig. 2 is a sectional view taken along line 2-2 of Fig. 1; and

Fig. 3 shows a modified form of my invention.

As illustrated, the preferred type of my invention may comprise a disk shaped grinding wheel ID of any suitable diameter and thickness, composed of abrasive grains, such as crystalline alumina or silicon carbide, bonded together into an integral grinding member by, any suitable bond, such as vitrified ceramic materials, rubber, sodium silicate or various resins, resinoids, etc. The disk has a substantially fiat annular grinding face l2, a supporting face l3, and the respective inner andouter peripheral faces l4 and I5. In order to rigidly and permanently support the grinding disk III for an abradlng operation, I preferably employ a backing H which is secured thereto by the means of a layer of vulcanized rubber compound. This backing may be composed of any suitablematerial and in my preferred construcbe pressed into a desired shape by a suitable heavy duty grinding operation tion comprises a moldable material which may method, and it is preferably composed of such v,mat erials as hard rubber of the nature of -ebonite or vulcanite, or various synthetic resinoids' including the well-known phenolic condensation products. vIn the presentinstance, the backing which is preferably separately manufactured by a suitable molding operation comprises a sub- .stantially flat, thin, disk shaped memberof the same outer diameter as the wheel L0 and of sufficient thickness to support the wheel, during a The grinding disk assembly is supported by a clamping member which in the present ;-i ns tance may comprise a rigid metal... plate .2!) firmly clamped against. the.backing or if desired. it

-,may be imbedded wlthin the backing during the molding operation. .,-This plate is shown.in,. the

formOia-disk of substantially the same diameter as the inner wheel periphery i4 and concentric therewith, but it will be appreciated that plate 20 may be of any suitable size and shape to properly engage and evenly distribute clamping forces throughout the backing. If desired, a suitable reinforcement, such as a wire screen 22, may be imbedded within the backing during the molding operation to strengthen it and aid in providing a relatively thin but substantially rigid backing for the disk. The backing is provided with two opposed faces 23 and 24 which are illustrated as substantially fiat, and the face 23 is arranged to be integrally secured to wheel face W by an intermediate layer of suitable cement, such as a plastic raw rubber compound 25 vulcanized in position under suitable influence of heat and pressure to form. either a hard or soft rubber of sufficient strength and adhesive characteristics to integrally unite the grinding wheel and backing. If the rubber compound contains 5% or less of combined sulphur by weight, a soft rubber is formed by vulcanization, and if more than 20% of sulphur is present, a hard rubber of the type of ebonite or vulcanite is formed. This rubber layer 25 is preferably relatively thin as compared to the thickness of the backing, but it must necessarily be of sufficient thickness to enter into the surface pore structure of the grinding wheel and firmly grip the rough projecting portions of abrasive and bond within the wheel face. y

In the construction of the preferred type of my invention, the backing is separately manufactured by a suitable molding operation and the reinforcing screen 22 is suitably located and impressed within the backing member I! during the molding operation. If desired, the clamping plate 20 may also be suitably located and imbedded within the backing, making it an integral member therewith. However, it will be appreciated that such a construction is not necessary, but merely a matter of convenience of assembly of the disk. Similarly, the plate 20 and wire screen 22 may be secured together by soldering, welding or. any other suitable method, and thereafter imbedded in the backing, which aids in providing further reinforcement. The surface 23 is cleaned and roughened by any suitable method. such as a well-known type of sandblasting operation. If desired, the face 23 may beprovided with suitable channels, or grooves or reentrant holes which pass through the backing to aid the vulcanized rubber compound in firmly adhering thereto. I

A layer of plastic raw rubber compound 25 of suitable consistency and containing the required 7 amount of sulphur and, if desired, a suitable vui-" canization accelerator, is placed between the backing and the grinding wheel in engagement ',with surfaces and 03 respectively. Suitable 'pressureis applied to "force the wheel and backing-towards each other, causing the raw plastic rubbercompound to be compressed and'to deform. sufficiently to flow into the pore structure of the wheel face, and embrace the rough portions of 1 surfaces 23 and 13. While the rubber compound is thus compressed between the grinding wheel and the backing support, sufficient heat, such as 200 to 250 C., is applied to vulcanizetherubber the wheel from its backing, and the wheel may be used until substantially all of the abrasive material has been worn away.

By applying various pressures, the layer of raw rubber compoundmay be caused to impregnate the grinding wheel to any desired extent and thereby secure it to the backing with the required tenacity. If the backing I1 is composed of molded hard rubber and if the wheel bond is also composed of rubber, the intermediate layer of vulcanized rubber compound will intimately unite with the rubber wheel bond and that of the backing sothat a unitary structure is provided having a single inseparable bond throughout the entire body of the disk.

In order to demountably secure my grinding disk in operative position, I have provided a means whereby the grinding unit may be quickly and removably clamped to a suitable rotatable support. One method of accomplishing this, as illustrated, comprises a series of countersunk holes 30, which pass through the clamping plate 20 and backing I! as shown, whereby screws 32 may be employed to secure the grinding unit to any suitable rotatable support. It will be appreciated that various other clamping .devices such as bolts, studs, or other suitable members may be employed to removably clamp the backing member to any suitable rotatable support in any convenient manner, but it is essential that the clamping devices must engage the plate 20 which serves to distribute the clamping and supporting forces evenly throughout the backing and thus prevents the clamping devices from tearing loose from a relatively friable backing material. In the present instance, three equally spaced countersunk holes pass through the clamping plate 20 and lie within the central wheel hole, whereby the clamping screws 32 are easily accessible through the wheel hole to quickly, secure the grinding unit in position, and their clamping pressures are distributed throughout the backing.

One convenient type of support to which my grinding unit may be removably secured may comprise a disk shaped member 34 supported for rotation with a driving shaft 35 and having suitably located threaded holes arranged to receive the clamping screws 32. It is not believed necessary to illustrate this rotatable support in detail, since it does not comprise a part of the present invention.

As shown in Fig. 3, a modified construction of my invention employs a reinforced backing composed of hard rubber of the general type of ebonite or vulcanite whichis directly vulcanized to a grinding wheel face without employing any intermediate layer of rubber compound, as is the practice in my preferred method of construction. In this modified construction, a clamping plate 40 corresponding with plate 20 of my preferred construction is suitably and temporarily supported in position in any convenient manner relative to surface l3 of grinding wheel I II and reinforcing wires 41 corresponding with wires 22 placed on plate 40 in the position illustrated. A layer of plastic. raw vulcanizable rubber compound 42 having a desired sulphur content and, if desired, a suitable vulcanization accelerator, is then placed upon wire screen. Suitable pressure is applied evenly over the entire sheet of plastic rubber compound to force it through the screen and into positive deformable engagement with wheel surface l3, thereby causing the screen rubber compound and causing the rubber compound to flow into the open pore structure of grinding wheel surface I3 to a desired extent and embrace the rough portions therein.

While the plastic raw rubber compound is thus compressed and held in positive engagement with the grinding wheel and the reinforcing members, suflicient heat such as 200 to 250 C. is applied to vulcanize it in position into a hard non-deformable material of the nature of ebonite or vulcanite, thereby providing a rigid wheel backing member which is integrally bonded to the grinding wheel lll,.forming an inseparable unit therewith. It has been found that a backing of this type has a tensile strength fully as great as that of the wheel bond and that it will grip the wheel with so great a tenacity that a heavy duty grinding operation will not tend to separate the wheel therefrom. Hence, a grinding operation may be performed with a disk as long as any of the abrasive material remains. The backing may be caused to flow into the port structure of the grinding wheel to any desired depth, dependent upon the pressures applied, and hence said backing may be caused togrip the grinding wheel with any desired tenacity. A grinding disk of this modified type would be demountably secured to a rotatable support in the same manner as shown in my preferred type of construction.

Whereas thebacking members disclosed in this invention are relatively easy to construct and inexpensive as compared to the grinding wheels which they support, it will be appreciated that, if desired, when the grinding wheel has been entirely worn away therefrom, said backing members may again have grinding wheels mounted thereon by means of an intermediate sheet of plastic raw rubber compound which is vulcanized in position as described in my preferred type of invention. However, due to the low cost of my backing, it is usually thrown away when the grinding wheel has been completely worn away, and a new grinding unit is purchased, thereby obviating the necessity and inconvenience of returning the backing to the factory and having a new grinding wheel installed thereon.

While I have specifically described the present invention as particularly adaptable to the manufacture of an abrasive wheel and a method of demountably securing it in position to perform a grinding operation, it will be apparent to those skilled in the art that various other bonded abrasive articles may be easily produced and secured in abrading position in the same manner. For example, a bonded abrasive body having a suitable abrading surface and commonly referred to as a rubbing block may be permanently vulcanized to a suitable backing in-the same manner as employed for a grinding disk, and suitable clamping devices may be arranged to engage clamping plates engaging the backing material. Such modifications or substitutions of my invention as lie within the scope of the appended claims are to be considered as embodied in the above specification.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A grinding wheel comprising a substantially porous body of bonded abrasive grains having a central hole therethrough, a backing therefor and plate 40 to become suitably imbedded in the tends across the wheel hole and has a face engageable with a wheel support, a clamping plate remote from said face which is imbedded within the backing and located within the wheel hole to secure the same against the wheel support, and means engageable with the plate for clamping the wheel assembly in position, whereby the backing distributes the clamping and driving forces between the wheel and its support.

2'. A grinding wheel comprising a porous body of bonded abrasive grains having a central hole therethrough, a separately manufactured molded backing therefor, a reinforcing wire screen embedded within the backing, said backing extending across the wheel hole and having an inner supporting face and an outer face engageable with a wheel support, an intermediate layer of vulcanized rubber impregnating the surface pores of the abrasive body and integrally securing the backing thereto, a clamping plate within the wheel hole and embedded within the inner backing face, and means engageable withsaid clamping plate to demountably secure the grind ing wheel on its support.

3. A grinding wheel comprising a cylindrical body of bonded abrasive grains having a central hole therethrough and a substantially flat annular supporting face, a rigid, disk-shaped, hard rubber backing vulcanized to said abrasive face, said backing extending across the wheel hole and having an outer face engageable with a wheel support, a clamping plate within the wheel hole and-integrally secured to the inner face of the rubber backing, and means engageable with the plate to demountably secure the wheelon the support in grinding position, said clamping plate and backing being so located relative to the abrasive body that all of the abrasive material therein is available for grinding operations.

4. A grinding wheel comprisinga porous body of bonded abrasive grains having a central hole therethrough and an annular supporting face, a rigid disk shaped hard rubber backing therefor which is vulcanized to the supporting face and has an outer face engageable with a wheel support, a reinforcing wire screen embedded within the backing, a clamping plate within the wheel hole embedded within the backing, means integrally securing the reinforcing screen and plate together 'as a unit, and means engageable with the plate to demountably secure the grinding wheel on the support.

, DUANE E. WEBSTER. 

